Balance charging battery pack one-half at a time?

Question

I'm trying to wrap my head around how I need to go about balancing charging a few NiMh battery packs.

I'm using a HiTec x4 charger, which supports balancing charging up to 6 cells at a time. However, the battery packs I'm working with have 12 cells welded together in series. 12 x 1.2v cells, for a total of 14.4v (actually ~17v fully charged).

I attempted to connect the 6 charging leads to the positive ends of the last 6 cells (closest to overall negative), and the 1 negative lead to the overall negative of the pack. However, this causes the charger to throw a 'Connection break' error, which I'm assuming is caused by the other 6 cells, even though they 'sit behind' the cells I'm attempting to balance charge?

How should I go about balance charging these 12 cell packs with a 6 cell balance charger, given I'm not able to break the weld without damaging them? Should I connect the positives leads to every other cell, and balance charge them as 6 x 2.4v "cells" instead? My worry with that is the charger might damage the cells, as it's expecting 1.2v NiMh cells, and I'm giving it 2.4v cells instead.

Any ideas?

Thanks in advance.

Answer 1

I've just come to learn that NiMh batteries don't need to be balanced in the way that Li-Po or Li-ion battery do. Essentially, to balance the cells you just have to slow-charge at around C/10 for a good 14-15hrs. This works because NiMh cells don't get damaged while slow-charging, even once full. This will eventually bring all the cells up to the same voltage.

Also, my charger was throwing the Connection break error because I had the wires connected the wrong way. Once I figured that out, I realized that the charge settings were wrong anyway, and I wasn't really 'Balance charging'. It turns out the charger only shows the balanced charging option when the 'Li-Po' battery type is selected. shrug

Now onto slow-charging the packs.